A major study released Monday puts the total number of Christians worldwide at 2.18 billion, or 31.7 percent — nearly a third — of the estimated global population of 6.9 billion. “Christians are also geographically widespread...

PARIS — The world population will reach seven billion later this year, with increases in the number of people in Africa off-setting birth rate drops elsewhere, according to a new French study published Thursday. Looking much further ahead, the...